Implementing resistance defect performance mitigation using test signature directed self heating and increased voltage

ABSTRACT

A method and system are provided for implementing resistive defect performance mitigation for integrated circuits. A test is generated for identifying resistive defects. A first self heating repair process is performed for repairing resistive defects. Testing is performed to identify a mitigated resistive defect and a functional integrated circuit. Responsive to identifying a resistive defect not being mitigated and a functional integrated circuit, a second repair process is performed, then testing is performed again.

This application is a continuation application of Ser. No. 14/750,471filed Jun. 25, 2015.

FIELD OF THE INVENTION

The present invention relates generally to the data processing field,and more particularly, relates to a method and system for implementingresistance defect performance mitigation for integrated circuits usingtest signature directed self heating and increased voltage.

DESCRIPTION OF THE RELATED ART

New semiconductor technologies afford enhanced densities, performanceand energy efficiencies but are often plagued with low yields and/orperformance issues. Functional yield issues and more often performanceissues, particularly early in the development time line are majorimpediments to system development schedules.

Performance of early user semiconductor hardware is often gated bydefects that add significant resistance, often in contacts to diffusionsand/or vias between metal planes.

A need exists for an effective method and system for implementingenhanced manufacturability, yield and performance of early developmentsamples of integrated circuits by identifying and repairing resistivedefects before the sample integrated circuits are supplied to systemdevelopers.

SUMMARY OF THE INVENTION

Principal aspects of the present invention are to provide a method andsystem for implementing resistive defect performance mitigation forintegrated circuits using test signature directed self heating andincreased voltage. Other important aspects of the present invention areto provide such method, and system substantially without negativeeffects and that overcome many of the disadvantages of prior artarrangements.

In brief, a method and system are provided for implementing resistancedefect performance mitigation for integrated circuits. A test isgenerated for identifying resistive defects. A first self heating repairprocess is performed for repairing resistive defects. Testing isperformed to identify a mitigated resistive defect and a functionalintegrated circuit. Responsive to identifying a resistive defect notbeing mitigated and a functional integrated circuit, a second repairprocess is performed, and testing is performed again.

In accordance with features of the invention, the first self heatingrepair process includes repeatedly switching a signal on the circuitpath containing the resistive defect at a selected frequency and aselected voltage, such as at or perhaps slightly above a maximumfrequency at which the integrated circuit will function for asignificant duration, for example on the order of microseconds allowingmillions of switches.

In accordance with features of the invention, the repeated switchingnominally is done at an elevated voltage to enhance the amount oflocalized heating and stressing of any residual dielectric films in theresistive defect.

In accordance with features of the invention, repairing resistivedefects includes for example, repairing resistive connections incontacts and vias, or a high resistance open defect present in aninternally embedded interconnect.

In accordance with features of the invention, an appropriate voltage foruse of the integrated circuit is applied to the defect node, and testingis performed to identify a mitigated resistive defect and a functionalintegrated circuit.

In accordance with features of the invention, the second repair processincludes for example, a laser utilized to enhance the local heating, orproviding incremental voltage steps and repeating until a maximumvoltage is reached.

In accordance with features of the invention, responsive to identifyinga resistive defect being mitigated and a functional integrated circuitbeing identified, a successful repair is identified. Responsive toidentifying a resistive defect being mitigated or not mitigated, when afunctional integrated circuit is not identified, the integrated circuitsample under test is discarded.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention together with the above and other objects andadvantages may best be understood from the following detaileddescription of the preferred embodiments of the invention illustrated inthe drawings, wherein:

FIG. 1 is a block diagram of an example computer system for implementingresistance defect performance mitigation for integrated circuits usingtest signature directed self heating and increased voltage in accordancewith preferred embodiments;

FIGS. 2A, 2B, and 2C are flow charts illustrating example steps forimplementing resistance defect performance mitigation for integratedcircuits using test signature directed self heating and increasedvoltage in accordance with preferred embodiments; and

FIG. 3 is a block diagram illustrating a computer program product inaccordance with the preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description of embodiments of the invention,reference is made to the accompanying drawings, which illustrate exampleembodiments by which the invention may be practiced. It is to beunderstood that other embodiments may be utilized and structural changesmay be made without departing from the scope of the invention.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

In accordance with features of the invention, a method and system areprovided for implementing resistance defect performance mitigation forintegrated circuits using test signature directed self heating andincreased voltage in accordance with preferred embodiments.

Having reference now to the drawings, in FIG. 1, there is shown anexample computer system generally designated by the reference character100 for implementing resistance defect performance mitigation forintegrated circuits using test signature directed self heating andincreased voltage in accordance with preferred embodiments. Computersystem 100 includes one or more processors 102 or general-purposeprogrammable central processing units (CPUs) 102, #1-N. As shown,computer system 100 includes multiple processors 102 typical of arelatively large system; however, system 100 can include a single CPU102. Computer system 100 includes a cache memory 104 connected to eachprocessor 102.

Computer system 100 includes a system memory 106, an operating system108, a test interface and test generator 110 and a resistive defectperformance mitigation control 111 in accordance with preferredembodiments of the invention and a user interface 112.

In accordance with features of the invention, the test interface andtest generator 110 and the resistive defect performance mitigationcontrol 111 are provided with an integrated circuit sample under testfor implementing resistance defect performance mitigation for integratedcircuits. Functional and performance testing of early user semiconductorhardware often focuses on identifying systemic failures and theunderlying frequency limitations. This invention further identifiesintegrated circuit samples having substandard performance due to one ormore resistive defects and defines a methodology to repair defects,recovering at least some integrated circuit samples otherwise unusablefor high performance development applications.

In accordance with features of the invention, the test interface andtest generator 110 and the resistive defect performance mitigationcontrol 111 implement techniques for identifying slow paths, such ascycle limiting logical or storage element path. Such techniques haveadvanced utilizing built in self test as well as application programsover the last several technology cycles. Conventionally once a slow pathhas been identified, the offending semiconductor is normally relegatedto the scrap pile or is utilized in some limited application where fullperformance is not required.

Methods of the invention mitigate resistive defect utilizing selfheating, optionally including another repair process using an externalsource, such as local laser heating during wafer performance testing.The resistive defects are most often related to openings, an undersizedvia or contacts and/or via or contacts with some residual insulatingfilm. Undersized contacts and/or vias that lead to resistive defects andexcessive delay frequently limit the ability of a semiconductorfabricator to provide development hardware at the performance targets ina timely manner. Defects are common as new lithography masks are broughtonline in fabrication, particularly those masks used before sufficientprocess window experimentation can be performed to optimize a givenreticle and lithography exposing tool to a particular design. The mostcommon defects that arise from this relative process/design interactionimmaturity are resistive, but not completely open connections incontacts and vias. These defects are most frequently caused by anundersized opening in the dielectric down to the underlying conductivesurface, for example, due to print or etch issues. Note these undersizedopening are often accompanied by a reduction in volume of theelectromigration mitigating liner films, often TiN.

In accordance with features of the invention, the test interface andtest generator 110 and the resistive defect performance mitigationcontrol 111 repair resistive defects via a novel self heating and/orexternal point heating technique after defects are identified utilizingtraditional means, nominally by application based maximum frequencylimiting path analysis. Once a defective connection is identified,repeatedly switching a signal to this defective connection at or perhapsslightly above the maximum frequency at which it will function at theselected voltage for a significant duration, such as on the order ofmicroseconds allowing millions of switches in an attempt to mitigate theresistive defect. This repeated switching is nominally done at elevatedvoltage to enhance the amount of localized heating and stressing of anyresidual dielectric films in the connecting area. Also a laseroptionally is utilized to enhance the local heating. Note all othercircuits can be power gated, clock gated or at least functionally gatedto avoid introducing new defects to previously fully functionalsemiconductor circuits. Typical defects that can be mitigated with thistechnique include oxidized liner issues, undersized contact or viasystemic issues. Physical failure analysis on one die can often indicatethe exact failing contact on another die, aiding this recoverytechnique.

In accordance with features of the invention, the test interface andtest generator 110 and the resistive defect performance mitigationcontrol 111, for example, provide elevated temperature, bias andswitching coupled with the unintentionally thin liner film associatedwith an undersized or malformed dielectric opening that allows smallamount of conductor (normally copper) to migrate from one conductorplane to another greatly reducing the resistance in the connection andallowing enhanced performance after this technique is utilized. Thesuccess rate of this new repair process typically is far less than 100%but is desirable with a success rate, for example, as low as 10%.

System memory 106 is a random-access semiconductor memory for storingdata, including programs. System memory 106 is comprised of, forexample, a dynamic random access memory (DRAM), a synchronous directrandom access memory (SDRAM), a current double data rate (DDRx) SDRAM,non-volatile memory, optical storage, and other storage devices.

I/O bus interface 114, and buses 116, 118 provide communication pathsamong the various system components. Bus 116 is a processor/memory bus,often referred to as front-side bus, providing a data communication pathfor transferring data among CPUs 102 and caches 104, system memory 106and I/O bus interface unit 114. I/O bus interface 114 is further coupledto system I/O bus 118 for transferring data to and from various I/Ounits. As shown, computer system 100 includes a storage interface 120coupled to storage devices, such as, a direct access storage device(DASD) 122, and a CD-ROM 124. Computer system 100 includes a terminalinterface 126 coupled to a plurality of terminals 128, #1-M, a networkinterface 130 coupled to a network 132, such as the Internet, local areaor other networks, and a I/O device interface 134 coupled to I/Odevices, such as a first printer/fax 136A, and a second printer 136B.

I/O bus interface 114 communicates with multiple I/O interface units120, 126, 130, 134, which are also known as I/O processors (IOPs) or I/Oadapters (IOAs), through system I/O bus 116. System I/O bus 116 is, forexample, an industry standard PCI bus, or other appropriate bustechnology.

Computer system 100 is shown in simplified form sufficient forunderstanding the present invention. It should be understood that thepresent invention is not limited to the illustrated arrangement ofcomputer system 100.

Referring now to FIGS. 2A, 2B, and 2C, there are show flow chartsillustrating example steps for implementing resistance defectperformance mitigation for integrated circuits using test signaturedirected self heating and increased voltage in accordance with preferredembodiments. In FIG. 2A, example steps start as indicated in a block200. As indicated in a block 202, a test is generated for identifyingresistive defects. An identified resistive defect location is isolatedusing power and/or clock gating as indicated in a block 204. Asindicated in a block 206, a first self heating repair process isperformed for repairing resistive defects. For example, switching a nodeof the resistive defect location at a selected frequency and a selectedvoltage for a set duration is performed at block 206. The selectedfrequency is, for example, at or perhaps slightly above a maximumfrequency at which the integrated circuit will function for a durationon the order of microseconds allowing millions of switches. The repeatedswitching at block 206 nominally is done at an elevated voltage toenhance the amount of localized heating and stressing of any residualdielectric films in the connecting area.

As indicated in a block 208, an appropriate voltage for use is appliedto the defect node, and testing is performed to identify a mitigatedresistive defect and a functional integrated circuit. Operationscontinue at a decision block 210 in FIG. 2B following entry point A.

In FIG. 2B, checking is performed to identify a mitigated defect asindicated in a decision block 210. When a mitigated defect isidentified, checking is performed to identify if the part stillfunctions as indicated in a decision block 210. When a functionalintegrated circuit is identified, a successful repair is identified andthe integrated circuit is passed for use. When a mitigated defect is notidentified, checking is performed to identify if the part stillfunctions as indicated in a decision block 216. Responsive toidentifying a resistive defect being mitigated or not mitigated, when afunctional integrated circuit is not identified, the integrated circuitis discarded as indicated in a block 218. Operations continue at adecision block 220 in FIG. 2C following entry point B.

In FIG. 2C, when a functional integrated circuit is identified, checkingis performed to identify if at a maximum voltage as indicated in adecision block 220. If not at the maximum voltage, the voltage isincremented by a set step as indicated in a block 222 and operationscontinue at decision block 206 in FIG. 2A following entry point C. Untilthe defect is mitigated, incrementing the voltage by the set step isrepeated until the maximum voltage is provided at block 222. When themaximum voltage is identified at decision block 220, the defect locationis heated with an external source, such as a laser or the like, asindicated in a block 224 and operations continue at decision block 206in FIG. 2A following entry point C.

Referring now to FIG. 3, an article of manufacture or a computer programproduct 300 of the invention is illustrated. The computer programproduct 300 is tangibly embodied on a non-transitory computer readablestorage medium that includes a recording medium 302, such as, a floppydisk, a high capacity read only memory in the form of an optically readcompact disk or CD-ROM, a tape, or another similar computer programproduct. Recording medium 302 stores program means 304, 306, 308, and310 on the medium 302 for carrying out the methods for implementingresistive defect performance mitigation for integrated circuits usingtest signature directed self heating and increased voltage in system 100of FIG. 1.

A sequence of program instructions or a logical assembly of one or moreinterrelated modules defined by the recorded program means 304, 306,308, and 310, direct the computer system 100 for implementing resistivedefect performance mitigation for integrated circuits using testsignature directed self heating and increased voltage in accordance withthe preferred embodiments.

While the present invention has been described with reference to thedetails of the embodiments of the invention shown in the drawing, thesedetails are not intended to limit the scope of the invention as claimedin the appended claims.

1. A method for implementing resistive defect performance mitigation forintegrated circuits in a computer system comprising: providing a testgenerator for identifying resistive defects; performing a first selfheating repair process for repairing resistive defects; performingtesting to identify a mitigated resistive defect and a functionalintegrated circuit; and responsive to identifying a resistive defect notbeing mitigated and a functional integrated circuit, performing a secondrepair process, and repeating testing to identify a mitigated resistivedefect and a functional integrated circuit.
 2. The method as recited inclaim 1 wherein the first self heating repair process includesrepeatedly switching a signal to a circuit path containing the resistivedefect at a selected frequency and a selected voltage for a setduration.
 3. The method as recited in claim 2 wherein said selectedfrequency is approximately equal or slightly above a maximum frequencyat which the integrated circuit functions, and said set duration equalsa set number of microseconds allowing millions of switches.
 4. Themethod as recited in claim 2 wherein the repeated switching is providedat a set elevated voltage to enhance localized heating and stressing ofany residual dielectric films in the connecting area.
 5. The method asrecited in claim 1 wherein repairing resistive defects includes one ormore of repairing resistive connections in a contact, a via, and a highresistance defect present in an internally embedded interconnect.
 6. Themethod as recited in claim 1 wherein performing testing to identify amitigated resistive defect and a functional integrated circuit includesapplying an appropriate voltage for use of the integrated circuit to adefect node, and testing to identify a mitigated resistive defect and afunctional integrated circuit.
 7. The method as recited in claim 1wherein said second repair process includes at least one of using alaser to enhance the local heating, and providing incremental voltagesteps to a defect node and repeating until a maximum voltage is reached.8. The method as recited in claim 1 includes identifying a successfulrepair, responsive to identifying a resistive defect being mitigated anda functional integrated circuit being identified.
 9. The method asrecited in claim 8 includes discarding the integrated circuit,responsive to a functional integrated circuit not being identified.10-20. (canceled)